The crossover of 4$f$ localized magnetic moments at high temperatures into
itinerant states of heavy mass at low temperatures in Cerium-based heavy
fermion materials is a fundamental problem in condensed matter physics,
involving a temperature-dependent hybridization between the $f$ levels immersed
in a sea of conduction electrons (\textit{ce}). Due to the Luttinger theorem, this
hybridization leads to a Fermi surface (FS) enlargement at low temperature:
as the $f$ electrons become itinerant, their contribution to E$_{\mathrm{F}}$
increases.
We have studied the evolution of the heavy fermion FS in Ce2RhIn8 as a
function of temperature using angle resolved photoemission. We observed
topological changes that emerge at a temperature scale much higher than the
onset of the coherence character of the $f$ electrons. This behavior can be
related to the evolution of the electrical resistivity as a function of
temperature: as typically found for Kondo lattice materials, it first
decreases when temperature is lowered, but increases below $\sim $ 150K as
the magnetic scattering of the \textit{ce} by the localized $f$ electrons becomes larger
than the phonon scattering. It reaches a maximum and then drops when the
magnetic scattering becomes coherent for T$^{\ast} \sim $ 5K.
This multiple scale behavior of the $f$ electrons is in good agreement with a
recent theoretical study performed in the parent compound
CeRhIn$_{5}$ [1].\\[4pt]
[1] Choi et al, Phys. Rev. Lett. \textbf{108}, 016402.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2013.MAR.F19.14